Add mint monitor snapshot API and dashboard panel

[joelklabo]

Summary

• add a new mint_monitor GraphQL query that returns:
  • mint DB entry counts (mints, melts, proofs, promises, total)
  • recent request volume (mint + melt quotes over trailing 24h)
  • host-level disk and CPU snapshot metrics
• expose the query in the client MintService (loadMintMonitor)
• add a Mint Dashboard monitoring panel that surfaces the snapshot directly in the admin UI

Why

This is a focused contribution toward cashubtc/nutshell#556's monitoring requirement:

• "number of entries in the database"
• "number of requests in recent past"
• "free disk space" and "used CPU"

Validation

• npm run test:server -- src/server/modules/api/mint/monitor/mintmonitor.service.spec.ts
• npx eslint src/server/modules/api/mint/monitor/*.ts src/client/modules/mint/services/mint/mint.service.ts src/client/modules/mint/services/mint/mint.queries.ts src/client/modules/mint/types/mint.types.ts src/client/modules/mint/modules/mint-subsection-dashboard/components/mint-subsection-dashboard/mint-subsection-dashboard.component.ts
• npx prettier --check src/server/modules/api/mint/monitor/*.ts src/client/modules/mint/services/mint/mint.service.ts src/client/modules/mint/services/mint/mint.queries.ts src/client/modules/mint/types/mint.types.ts src/client/modules/mint/modules/mint-subsection-dashboard/components/mint-subsection-dashboard/mint-subsection-dashboard.component.ts src/client/modules/mint/modules/mint-subsection-dashboard/components/mint-subsection-dashboard/mint-subsection-dashboard.component.html src/client/modules/mint/modules/mint-subsection-dashboard/components/mint-subsection-dashboard/mint-subsection-dashboard.component.scss src/server/modules/api/api.module.ts

Notes

• Full npm run build exits early in this local environment (Node v25.2.1, project expects >=22 <23).
• The feature itself is covered by targeted server tests + lint/format checks above.